The use of metal oxides (MOs) in methanol-to-olefins (MTO) reactions has been described in detail in several publications, including U.S. Pat. Nos. 6,844,291, 6,906,232, 6,995,111, 7,166,757, 7,186,875, 7,199,277, 7,199,278, and 7,208,442, as well as U.S. Patent Application Publication Nos. 2005/0137439 and 2008/0103345.
One problematic aspect of MO use is the fact that not every example of a given chemical formulation is effective in generating the benefits ascribed to their use. For example, some samples of yttria MO (Y2O3) are virtually inactive as co-catalysts, while other examples may be effective.
We have previously disclosed that CO2 adsorption at 100° C. may be used to differentiate the various examples of MOs (U.S. Pat. No. 6,844,291). However, there is a possibility that CO2 can react stoichiometrically with the MO to form the respective carbonates, even in the absence of basic sites on the MO to, in effect, give a false reading of the potential activity of the MO as a lifetime extension co-catalyst in OTO (MTO) use.
A more specific and targeted probe of the basic sites would be useful in selecting both potential MOs and in directing the preparation steps to avoid inadvertently deactivating the MO prior to or during use. Therefore, there is a need to provide a method of selecting and monitoring the quality of the MO for use as a co-catalyst in OTO (MTO) reactions.